1. Field of the Invention
The present invention relates to a lens barrel, and more particularly to a lens barrel having a flare diaphragm mechanism.
2. Related Art Statement
Hitherto, a variety of flare diaphragm mechanisms of a type which is moved in the direction of the optical axis in synchronization with zooming of a photographing zoom lens have been suggested.
For example, a technological means disclosed in Japanese Patent Publication No. 58-42443 is arranged in such a manner that a flare diaphragm disposed between a movable lens frame and a fixed member is moved in a direction of the optical axis by an adequate quantity by utilizing a relative movement taking place between the fixed frame and the movable lens frame and a cam means.
Another technological means disclosed in Japanese Patent Publication No. 60-4102 is structured to have a flare diaphragm drive cam which can be independently operated from each lens group arranged to be moved due to zooming of the photographing zoom lens, so that the flare diaphragm is operated by the drive cam.
A technological means disclosed in Japanese Patent Laid-Open No. 56-80011 is structured in such a way that a friction member, which is fastened to a movable frame, and the flare diaphragm are connected to each other by friction, and the flare diaphragm is fastened between another movable frame and a fixed frame so that the flare diaphragm is moved by utilizing the frictional force.
The aforesaid conventional technology, for example, the technological means disclosed in Japanese Patent Publication No. 58-42443 requires a space in which the movable lens frame is moved by the fixed member and also requires a cam for driving the flare diaphragm.
The technological means disclosed in Japanese Patent Laid-Open No. 60-4102 requires a cam for driving the flare diaphragm in such a manner that the cam is interlocked with the cam for driving the lens group.
In either case, the following problems are encountered as compared with a structure having no flare diaphragm:
(1) A large space is required.
(2) A complicated mechanism is required, causing a defect to take place in assembling and the cost cannot be reduced.
Although the technological means disclosed in Japanese Patent Laid-Open NO. 56-80011 is able to overcome the problems (1) and (2), other problems arise in that a frictional member is required to generate the frictional force and that the flare diaphragm is undesirably separated from the movable frame due to shock or the like.